You contradict yourself. You have no way of knowing which are "empty" and which are not.
No I don't. I am just saying that an evil guy like Hitler cannot mouth words he does not believe so that God will say "Drat! Another evil guy saved because he uttered the secret words at the right time! I was going to send him to Hell, but he tricked me!". I am saying an empty confession is empty, and that someone cannot "beat the system". I expect a lot of deathbed confessions are of the empty variety, though not necessarily all.